Sildenafil is an ED medicine used to treat impotence. Sildenafil (Viagra) headache is a side effect of the ED medicine. 16-28% of men taking Sildenafil reported headaches. The headache stays as long as the effect of the ED medicine stays which is about 4 hours.
Learn more about cause, treatment, and prevention in this blog-
https://remedycounter.com/blog/viagra-headache/